1. Field of the Invention
The present invention relates to a body motion detection device, a pitch meter, a wristwatch-type information processing device, a method for controlling thereof, a control program, and a storage medium. The present invention particularly relates to technology for reliably determining pitch of a user from a detected body motion signal regardless of whether the user is walking or running.
2. Background Information
In a conventional pedometer for measuring the number of steps when a user is running or walking, a body motion signal is detected by an installed acceleration sensor (body motion sensor). As seen in FIG. 42, the obtained body motion signal is converted to a rectangular waveform, and the number of steps is determined from the body motion signal converted to the rectangular waveform. Specifically, when the body motion signal (analog signal) shown in the upper part of FIG. 42 is amplified and then converted to a rectangular waveform using a prescribed threshold value TH1, a pulse signal PS having the pulse shape shown in the lower part of FIG. 42 is obtained. However, since the characteristics of the waveform of the outputted signal are different between when the user walks with arms extended and when the user runs with arms bent, there are problems in that the number of steps cannot be accurately counted merely by converting the body motion signal to a rectangular waveform.
Therefore, in the pedometer shown in Japanese Laid-Open Utility Model Patent Publication No. H2-612 (Japanese Utility Model Patent Application No. S63-79116), a method is proposed wherein every time the number of pulses in a pulse signal PS is counted, a mask time of a certain interval is set whenever one pulse is counted. Accordingly, pulses are counted in units of two and the counted number is doubled to determine the number of steps. Thus, the precision of detection is improved.
However, in the above-mentioned conventional pedometer, the counted number cannot be doubled to determine the number of steps and improve the precision of detection if the mask time is not set such that the pulses are counted in a manner in which a single pulse is always counted in the mask time. Therefore, the mask time must be set depending on the walking speed or running speed (proportionate to pitch).
Specifically, when the pitch is 81 to 159 cycles/min, setting the mask time to 0.75 sec allows a single pulse to be included in the mask time, and the number of steps can accurately be determined by the method described above. However, when the pitch is 80 cycles/min or less, or 160 cycles/min or more, either no pulses are included at all in the mask time or a plurality of pulses are included, which has been the cause of errors. However, it is difficult to distinguish between a state of walking and a state of running by the pitch waveform alone, and the determinations are susceptible to error. Also, although the erroneous results can be prevented if the user chooses the operations of the pedometer between a state of walking and a state of running by manual operations every time the user uses the pedometer, problems occur in that ease of use is compromised.
Moreover, as in the above-mentioned conventional method, with a method of calculating the number of steps using rectangular waveform conversion, it has been a problem that when noise gets mixed in or when the operating direction and the direction of sensitivity of the sensor do not coincide, the body motion signal is not clearly outputted in accordance with the leg motion as shown, for example, in FIG. 43. In such cases, calculation results of the pitch contain large errors. More specifically, concerning the points originally meant to be counted (the timing shown by the arrow in FIG. 43), at point E where noise gets mixed in, the pulse is erroneously counted and the calculated pitch grows large in relation to the actual pitch. Conversely, at point NC, where the body motion signal has a low level, the pulse is not counted, and the pitch becomes small in relation to the actual pitch.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved body motion detection device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.